A Study on the Thermal Stabilities of the NiGe and Ni[sub 1−x]Ta[sub x]Ge Systems

The thermal stabilities of the Ni-silicide and Ni-germanide systems were compared, and that of the Ni 0.9 Ta 0.1 ∕ Ge alloy system was also studied. Although the NiSi film had a stable low sheet resistance ( R s ) in the formation temperature range from 300 to 650 ° C , NiGe exhibited an abrupt increase of R s from 500 ° C due to the severe agglomeration. The doping of the Ni film with Ta slightly improved the thermal stability of NiGe due to the formation of a Ta-rich layer on top of NiGe and subsequent reduction of the surface-free energy of NiGe with outside ambient. During the additional thermal annealing after NiGe formation, the germanide films formed from Ni – Ta alloy also exhibited slightly improved thermal stability characteristics as compared to the pure Ni-germanide system.